The overall long-term goal of this project is to improve the outcome of seizure surgery by the development of improved methods for the localization of seizure foci. It has clearly been demonstrated that when there is concordance between video/EEF telemetry (VET) and PET, or MRI, patients have an improved prognosis for seizure relief by seizure surgery compared to discordant studies. Unfortunately, approximately 50% of the patients with temporal lobe epilepsy (TLE), and 70% of the patients with neocortical epilepsy (NE) do not have concordant imaging studies. Preliminary studies utilizing MRS have demonstrated metabolic abnormalities in the epileptogenic zone with the focus defined by increased Pi and pH, and decreased NAA and PME. These preliminary studies have also demonstrated that these changes can be used to accurately predict the side of seizure onset (lateralization) with sensitivity in TLE as good as or better than PET. The goal of this application is to develop the combination of diagnostic measures which best predicts surgical outcome. To achieve this goal VET and the three imaging modalities employed in this study (PET, MRI, and MRSI) will be used to provide classification information. We will develop decision rules to determine which measures (e.g. VET, pH, Pi, PME, NAA, atrophy, increased signal intensity, hypometabolism) or combination of measures best predicts surgical outcome. It is expected that: 1) MRSI will provide better concordance with VET than MRI, or PET for TLE, 2) the best surgical outcome will be associated with the highest concordance between all modalities, 3) the abnormalities defined for the epileptogenic focus in TLE will also be true for NE. In conclusion, these results should lead to more effective preoperative evaluation for seizure surgery, providing a greatly improved diagnostic approach for evaluation of TLE & NE.